Although dietary guidelines have long advised eating a variety of foods, most nutrition research has focused on specific nutrients and their relationships to health and disease. The recent failure of several randomized trials to confirm results of observational studies linking specific nutrients to disease outcomes, and a growing understanding of the beneficial phytochemicals in the natural food supply, has redirected attention to the complexity and importance of the foods themselves. Studies identifying associations between diet quality and mortality are beginning to quantify the importance of eating a variety of healthful foods and are helping to refine that advice.